Methods of making polyvinylidene fluoride (PVDF) membranes and their use as filter media are known. See, for example, U.S. Pat. Nos. 4,203,847, 4,203,848 and 4,384,047. In the '047 patent there is disclosed a method of making "skinned" asymmetric PVDF ultrafiltration membranes having a surface layer with a multiplicity of very fine ultrafiltration pores (in the range of 0.0001 to 0.1 micron) and a support layer thicker than and having less resistance to fluid flow than the surface layer, the method comprising forming a solution of PVDF and a glycerol pore-former in triethylphosphate (TEP), casting a film, evaporating solvent, and immersing the cast film in a water or oil bath. Such membranes are not suitable for microfiltration because of their ultrafine pores. There still exists a need for a method of making thin, high flux, flexible hydrophobic membranes that are suitable for microfiltration (pores in the range of 0.1 to 5 microns) and capable of being rendered hydrophilic without any substantial sacrifice in flexibility or strength. These needs and others are met by the present invention, which is summarized and described in detail below.